GATE Mechanical Engineering Practice Quiz

Question 1

A plane wall 0.2 m thick with a thermal conductivity of 0.5 W/m·K has its inner face at 200 °C. Its outer face loses heat by convection to air at 30 °C with a coefficient of 10 W/m²·K. What is the steady heat flux through the wall?

Accepted Answer

340 W/m²

Question 2

A steel sphere of 50 mm diameter with k = 50 W/m·K is cooled with a convection coefficient of 100 W/m²·K. Using the characteristic length V/A, what is the Biot number?

Accepted Answer

0.017

Question 3

The steel sphere of the previous conditions has ρ = 7800 kg/m³ and c = 470 J/kg·K, with Lc = 0.00833 m and h = 100 W/m²·K. What is its lumped capacitance time constant?

Accepted Answer

306 s

Question 4

In a counterflow heat exchanger a hot stream cools from 100 °C to 60 °C while a cold stream is heated from 20 °C to 50 °C. What is the logarithmic mean temperature difference?

Accepted Answer

44.8 °C

Question 5

A black surface of 1 m² at 500 K exchanges radiation with large black surroundings at 300 K. What is the net rate of radiant heat loss?

Accepted Answer

3.08 kW

GATE Mechanical Engineering Group Discussion

Students preparing for GATE Mechanical Engineering

GATE Mechanical Engineering — Group Discussion